1. Field of the Invention
The present invention relates to an optical disc drive which can play back information recorded on and/or record information onto various types of optical discs and a method of discriminating the various types of the optical discs.
2. Description of the Prior Art
Optical disc drives which can playing back information recorded on and/or record information onto an optical disc such as a CD (compact disc), CD-ROM, CD-R or CD-RW are known in the prior art.
Among such optical discs, the CD, CD-ROM and CD-R are classified as high-reflectance optical discs due to the characteristics of their respective recording layers. Further, the CD-RW is classified as a low-reflectance optical disc.
Recently, optical disc drives which are capable of playing back information recorded on various types of high-reflectance optical discs with a single disc drive have been proposed. For example, an optical disc drive which can play back not only information recorded on a CD-ROM but also information recorded on a CD-R is known.
However, up to the present time, there has been no optical disc drive which is capable of playing back both high-reflectance optical discs and low-reflectance optical discs.
It is therefore an object of the present invention to provide an optical disc drive which is capable of easily and reliably playing back and/or recording various types of optical discs having different reflectances (i.e., high-reflectance optical discs and low-reflectance optical discs), and a method of discriminating such various types of optical discs.
In view of this object, the present invention is directed to an optical disc drive which can play back information recorded on and/or record information onto at least two types of optical discs having different reflectances. The disc drive comprises:
a rotational drive mechanism for rotating an optical disc to be loaded in the optical disc drive;
an optical pick-up having an objective lens, said optical pick-up emitting light beam onto the loaded optical disc and receiving the light beam reflected by the optical disc through the objective lens, to generate detection signals in response to the amount of the received light beam;
focus error signal generating means for generating a focus error signal based on the detection signals; and
optical disc discrimination means for discriminating a disc type of the loaded optical disc based on the amplitude of the focus error signal.
In this optical disc drive according to the present invnetion, the amplitude of the focus error signal varies depending on the reflectances of the respective optical discs. Specifically, in the present invention, the at least two types of optical discs include a high-reflectance optical disc and a low-reflectance optical disc.
According to the disc drive as described above, it is possible to play back information recorded on and/or record information onto various types of optical discs having different reflectances (i.e., high-reflectance optical discs and low-reflectance optical discs).
In the present invention, it is preferred that the focus error signal is produced by displacing the objective lens in the optical axis direction, and then the optical disc discrimination means discriminates whether or not the loaded optical disc is a high-reflectance optical disc or a low-reflectance optical disc based on the thus produced focus error signal.
Further, in the present invention, it is preferred that if the reflectance of a high-reflectance optical disc to be loaded in the optical disc drive is designated by xe2x80x9cxcex1xe2x80x9d and the reflectance of a low-reflectance optical disc to be loaded in the optical disc drive is designated by xe2x80x9cxcex2xe2x80x9d, then the value of xe2x80x9cxcex1/xcex2xe2x80x9d is greater than or equal to 2.5.
Moreover, in the present invention, it is preferred that the optical disc discrimination means discriminate whether or not the loaded optical disc is a high-reflectance optical disc or a low-reflectance optical disc by comparing an amplitude of the focus error signal or a vale corresponding thereto with a predetermined threshold value.
In the present invention, it is also preferred to further comprise means for setting recording conditions and/or playing back conditions corresponding to the type of the loaded optical disc based on the result of the discrimination by the optical disc discrimination means. This setting means sets recording and/or playing back conditions corresponding to a high-reflectance optical disc in the case where the loaded optical disc loaded is discriminated as a high-reflectance optical disc by the optical disc discrimination means, and sets recording and/or playing back conditions corresponding to a low-reflectance optical disc in the case where the loaded optical disc loaded in the optical disc drive is discriminated as a low-reflectance optical disc by the optical disc discrimination means.
In this way, the optical disc drive according to the present invention makes it possible to reliably record information onto various types of optical discs having different reflectances and/or playback information recorded on the various types of the optical discs.
In this case, the conditions to be set by the setting means may include a focus servo gain and/or a tracking servo gain.
Further, in the present invention, the optical disc discrimination means may have a further function for judging as to whether or not an optical disc is loaded in the optical disc drive.
In this way, it is possible to prevent the optical disc drive from starting the process for recording or playing back information when no optical disc is placed on the disc tray which has been moved from the eject position to the loaded position.
Furthermore, it is also preferred that the optical disc discrimination means judges as to whether or not the loaded optical disc is a low-reflectance optical disc in the case where no high-reflectance optical disc has been detected by the discrimination means.
Another aspect of the present invention is directed to a method of discriminating a disc type of an optical disc loaded in an optical disc drive which can play back information recorded on and/or record information onto at least two types of optical discs having different reflectances. This method comprises the steps of:
rotating the optical disc loaded in the optical disc drive;
emitting light beam from an optical pick-up onto the loaded optical disc and receiving the light beam reflected by the optical disc by the optical pick-up, to generate detection signals in response to the amount of the received light beam;
producing a focus error signal based on the detection signals; and
discriminating a disc type of the loaded optical disc based on the amplitude of the focus error signal which varies depending on the reflectance of the optical discs.
In this method, the at least two types of optical discs include a high-reflectance optical disc and a low-reflectance optical disc.
Further, in this method, the focus error signal is produced by displacing the objective lens in the optical axis direction, and then the loaded optical disc is discriminated as a high-reflectance optical disc or a low-reflectance optical disc based on the thus produced focus error signal.
Furthermore, in this method, it is preferred that if the reflectance of the high-reflectance optical disc to be loaded in the optical disc drive is designated by xe2x80x9cxcex1xe2x80x9d and the reflectance of the low-reflectance optical disc to be loaded in the optical disc drive is designated by xe2x80x9cxcex2xe2x80x9d then the value of xe2x80x9cxcex1/xcex2xe2x80x9d is greater than or equal to 2.5.
Moreover, in this method, It is preferred that the discrimination is carried out by comparing an amplitude of the focus error signal or a vale corresponding thereto with a predetermined threshold value.
Further, in the present invention, it is preferred that the discriminating step includes a first step for Judging as to whether the loaded optical disc is a high-reflectance optical disc or not, and a second step for judging as to whether the loaded optical disc is a low-reflectance optical disc or not, wherein the second step is carried out in the case where no high-reflectance optical disc is detected by the first step.
In this case, it is preferred that the focus servo gain at the first step is grater than that at the second step. Alternatively, the amplification factor for the focus error signal at the first step can be grater than that at the second step.
Furthermore, in the method of the present invention, it is also preferable to further comprise a step for Judging as to whether or not an optical disc is loaded in the optical disc drive.
The above described and other objects, structures and advantages of the present invention will be apparent when the following description of the preferred embodiment will be considered in conjunction with the appended drawings.